Thank you for reaching out to Constant Contact API Developer Support.
It looks like we've already followed up with you directly via email, but here is the information provided for visibility on the forum:
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As Microsoft Power Apps is a 3rd party product and not built or supported by Constant Contact, we are limited in the support we can provide, but will try to answer any questions to the best of our ability as they pertain to Constant Contact’s API endpoints and functionality.
Our current OAuth flows all require the State Parameter, so if you are not entering this value manually, then my best guess is that the program you are using may be generating it for you when submitting the request.
Authorization Request - Request Parameters
After taking a look at the public documentation for Power Apps, I wasn’t able to find where you might add/modify the State Parameter when configuring your OAuth settings. However, that doesn’t necessarily mean that there isn’t a way to do it.
Configure additional settings for OAuth 2.0 providers
You'll want to reach out to Microsoft to verify whether this functionality is available in their platform and how to configure it.
Open a Support Request for Power Apps with Microsoft:
Please have a look and let us know if you have any other questions!
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